Forest fires have increased in incidence in the recent past. Most fires, until recently, were fought with water only. However, the use of water has had a limited effect upon the retardation of forest fires due to inaccessability and the relative slowness of delivering water to the fires. Often, water runs off dry ground and away from the fire area.
Fire retardant material has been dropped from airplanes or helicopters onto forest fires. Fire retardants may be classified as short-term or long-term retardants. For example, U.S. Pat. No. 3,553,128 describes a short-term fire retardant material which relies solely upon water to retard combustion. Long-term retardants contain a chemical that retards flaming combustion after the water has evaporated.
Currently, the most commonly used retardants are ammonium phosphate salts. Often, long-term retardants are thickened with additives such as polysaccharides. However, numerous problems have been encountered in using existing long-and short-term retardants. Existing retardants have a short shelf-life, cannot be easily mixed properly, decay under high-temperature conditions or cannot be used with hard water or sea water. Furthermore, although these chemicals can retard fires, they cannot extinguish them. Current retardants merely decrease the rate at which the fires spread, but cannot create a barrier to prevent the fires from spreading at all. Retardants create a "fire break" or absence of fire in their vicinity but can not provide an even fire barrier. Fires can create a path to penetrate the firebreak and continue to burn forest past the fire break point. Furthermore, the retardants could not penetrate moss and duff on the ground of the forest, which provide fuel for the fire.
Thus, the need for an effective fire retardant material which could create a long-lasting fire break was clear.